The present invention relates to cooling equipment for an integrated circuit chip.
For integrated circuits (IC) mounted on a print wired board and a ceramic substrate, air cooling equipment is usually used. In such equipment, the cooling air is blown against the heat sink or the case. However, for the following reasons, use of air as a cooling medium to carry the heat from an IC has some disadvantages and problems.
The first reason is the necessity for relatively large air conditioning capability to lower the air temperature because the temperature difference between the heat sink or IC case and air is large. A large amount of air must be sent into the unit to remove the heat generated by the unit, since the heat capacity of the air is small. Further, modern data processors comprise high density and high power ICs to speed up processing and signal transmission, thus increasing both the quantity of heat and the density of heat generated. Accordingly, the air conditioner needs high capacity and, inside the unit, an air blower must give high airflow and exhausting ability to compensate for the reduction of the air path inside the unit caused by high density mounting of components and to exhaust the great amount of heat from the unit. The necessity for an air conditioner with high cooling capacity and large throughput also can cause excessive noise. Further, since it is difficult for the air stream to be distributed equally in the unit, the temperature of the ICs may rise locally, causing deterioration of the reliability of the unit.
To solve these defects, an example of liquid cooling unit is proposed in the article entitled "A Conduction-Cooled Module for High-Performance LSI Devices", by S. Oktay et al, published in the IBM J. Res. Develop., Vol. 26, No. 1, January 1982, pages 55-66. Referring to FIG. 1(b) of the article, the surface of a chip mounted on the substrate is contacted by spring loaded piston so that the heat from the chip is conducted to a "hat" via the piston and helium. The hat is cooled by cooling medium utilizing a water cooled cold plate heat sink.
The module as proposed by Oktay et al has the following shortcomings. First, since the semiconductor chip mechanically contacts the piston, it is impossible to achieve electrical isolation between the chip and the cooling medium. As the cooling medium is electrically connected to the earth terminal of a compressor or a pump for sending out the cooling medium, if a conductive cooling medium is used, the chip can misoperate. Next, a vibrating system expressed in the equation of W.sub.o =.sqroot.K/m (W.sub.o shows sympathetic angular frequency, K shows constant of the spring, and m shows mass of the piston) is made up by the piston and the spring. If the power including a sympathetic frequency element from outside puts pressure on the module, vibration of the piston can destroy the chip. Finally, creep transformation can occur because the solder for connecting the substrate is always under mechanical pressure. This transformation is particularly significant in the case of using solder with a low melting point.